如何用除零（Python，numpy）以外的其他数组的所有数字替换数组的所有数字？

Question

I have two arrays like these:

a = [[1,2,-3],[4,5,-6],[7,8,9]]
b = [[2,-5,0],[0,4,8],[-2,1,0]]

Every number of "a" should be replaced with the one from "b", except of those, where the number of "b" is 0:

result = [[2,-5,-3],[4,4,8],[-2,1,9]]

My current solution takes way too long:

for row in range(len(b)):
    for column in range(len(b[row])):
        if b[row][column] != 0 or b[row][column] != -0:
            a[row][column] = b[row][column]

Btw. is the "b[row][column] != -0" necessary? Since there are sometimes "0"s and sometimes "-0"s in b.

Is there a fast way? Thanks.

Answer 1

Just use np.where()

a = np.array(a)
b = np.array(b)
a = np.where(b == 0, a, b)

If you want to get fancy and save memory, use np.place()

np.place(a, b != 0, b[b != 0])

EDIT: Since 0 == -0 evaluates True , you don't need any other checks

Answer 2

一种可能性：

a[np.where(b !=0)] = b[np.where(b !=0)]